1. Field of the Invention
The present invention relates to an image pickup apparatus and a lens device, which are provided with a barrier for protecting the front face of a lens barrel.
2. Description of the Related Art
Conventionally, there have been proposed various types of barriers each for opening/closing the front face of a camera, so as to protect a photographic lens of the camera.
In image pickup apparatuses provided with barriers of the above-mentioned kind, most of the barriers have conventionally been configured to vertically or laterally open/close flat plates disposed in front of a lens barrel, as disclosed in Japanese Patent Laid-Open Publication No. 2006-98486.
Further, Japanese Patent Laid-Open Publication No. 2002-258133 discloses a technique in which a barrier, which is divided into an upper part and a lower part, is opened and closed along a dome-shaped path about a point on the axis of the lens barrel.
FIGS. 28A and 28B are perspective views of a conventional barrier mechanism disclosed in Japanese Patent Laid-Open Publication No. 2002-258133. FIG. 28A shows a state in which a barrier is closed, and FIG. 28B shows a state in which the barrier is open. This barrier is formed into a spherical shell shape having a center at a point on the optical axis of a lens (i.e. the point on the axis of the lens barrel). Further, as mentioned hereinbefore, the barrier is divided into an upper half barrier 62a and a lower half barrier, and these barriers can be rotated about respective rotary shafts (one of which is denoted by 68m) which are supported on bearings provided in laterally symmetrical relation on the opposite sides of the lens barrel and have the same rotational axis perpendicular to the optical axis and extending through the point on the optical axis.
Further, on the front face of the lens barrel, there is provided an opening/closing ring 21 for opening and closing the barrier, in a manner rotatable about the optical axis of the lens. When the opening/closing ring 21 is rotated, the upper half barrier 62a and the lower half barrier operate in respective opposite directions with respect to the optical axis, whereby the barrier is opened and closed.
However, the above-described conventional barrier is comprised of the upper half barrier 62a and the lower half barrier, and hence it is required to secure a large space for the upper half barrier 62a and the lower half barrier in the barrier open state, which is an obstacle to size reduction.
Further, the upper half barrier and the lower half barrier are configured to rotate about the same rotational axis, and hence, in a case where the upper half barrier and the lower half barrier are each further divided in two, i.e. the barrier is comprised of four barrier blades for size reduction, a rotary shaft provided at each of the left and right sides of the lens barrel requires a thickness corresponding to the four barrier blades. Therefore, the thickness of the barrier forms an obstacle to size reduction.
Furthermore, the barrier constructed as above needs a large rotary ring for driving the upper half barrier and the lower half barrier on the front side of the lens barrel, which lowers the degree of freedom in layout, and also becomes an obstacle to size reduction.